The "k" sound at the end of multisyllable short-vowel words is spelled with a "c."
When a suffix beginning with a vowel is added to these words, the "c" ending is changed to "ck." Remember what we learned on page 40? "It's 'k' and not 'c' followed by 'i' or an 'e.'"
(Sigh.....Why is spelling SO COMPLICATED?)